Marine Spatial Planning (MSP) implies the ability to ‘objectify’ the distribution of offshore activities on the basis of information. Geographical information is essential in this process, but its role is still little discussed. Yet, from its construction to its circulation, geo-information implies a series of choices which are far from being ‘objective’ or neutral. This presentation aims to examine the role of geo-information and associated geo-technologies in MSP in order to identify the critical points to be considered. Using an empirical approach (fieldwork, interviews, grey literature) in three fisheries-related case studies in Senegal (the St-Louis region, the Kayar MPA and the Saloum delta), the study shows a fairly wide range of informational issues related to MSP, from which we sum-up three main results. Firstly, there is a chronic lack of geographical information in general, and there is a particular need to better document both the interactions between uses (especially in regard to the growing offshore oil and gas activity) and the various scales at which these ones play. Secondly, while we need to be able to document the fishing practices and grounds, the ways of documenting them (in this case, mapping them) can be diverse. Notably fishers can themselves be part in the construction of data. Finally, the importance of being able to reconstruct the dynamics of human activities over a longer period of time, as well as the limits to taking fisheries into account solely as economic activities, appear very important. Indeed, fisheries are sometimes mainly self-subsistence activities and, whatever the form of fishing, they almost always have dimensions (identity, culture, etc.) that go beyond the framework of the market economy. It is therefore necessary to take a closer look at the way in which the diverse and complex ‘reality’ of fisheries is coded, translated and transcribed into geographical information that can be simplifying and embedded into MSP processes.